Joe, if you have access to or want to order a1947-1954 Truck, Factory Assembly Manual you will find a discription of the welding and soldering of the cabs in Section 1, starting with Sheet 46.00 and for about another ten or so pages. Also in Section 14, Sheet 12.00 are the complete "Underbody Protective Coating Instructions" which outlines the undercoating procedures from the factory. Body Brackets, Underside of Floor Panels, Cowl Side, Cowl Side Rail, Fender Flanges.
So yes, they did undercoat from the factory where it is shown in the pictures that I linked you to.
Denny Graham
Sandwich, IL
